The purpose of the proposed research project is to provide an analysis of the kinds of syntactic information that aphasic patients have difficulty representing for the purpose of sentence comprehension. This overall objective incorporates the following question: Is the same form of syntactic limitation present in all aphasia, or is there a limitation unique to patients with Broca's aphasia - that is, a specific limitation that follows from left anterior brain damage? The general thrust of the research will be to apply theoretical linguistic principles to try to account for sentence types that aphasic patients have difficulty understanding. The focus will be on aphasic patients' ability to understand various non-canonical sentence forms that have been theorized to involve constituent movement via the operation known as a grammatical transformation. The moved constituent is claimed to leave an empty position behind, called a "trace", with which it is coindexed. In this framework, the aphasic limitation - possible a limitation only for Broca's aphasic patients - is hypothesized to be an inability to represent "traces". As a result, the patients are faced with mapping thematic roles (such as agent, beneficiary, goal) onto incomplete syntactic structures, and are, therefore, forced to resort on non-grammatical comprehension strategies that do not always work. Three studies of this hypothesis are proposed, each dealing with a different set of sentence types that establish different patterns of constituent movement. In each case, the paradigm is one of sentence-picture matching. This program of study should provide a precise characterization of aspects of grammatical impairment in aphasia, thereby providing the basis for developing finer-grained diagnostic tools.